Add popular user fields to GraphQL

What does this MR do and why?

For an integration we're building with our community platform (Common Room) we need to extract these popular social fields using GraphQL.

This MR adds those popular user fields to GraphQL.

Related to: https://gitlab.com/gitlab-org/community-relations/gitlab-common-room-api-source/-/merge_requests/1

Screenshots or screen recordings

How to set up and validate locally

Edit your profile to add:

• Bio
• Twitter username
• LinkedIn profile name
• Discord user id (17 digits)
• Organization
• Job title

Run the following in GraphiQL:

query {
  currentUser {
    id
    username
    name
    avatarUrl
    publicEmail
    linkedin
    twitter
    discord
    organization
    jobTitle
    location
    createdAt
  }
}

MR acceptance checklist

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